1. Field of the Invention
This invention relates to bubble (magnetic domain) memories and more particularly to a storage loop bubble memory organization with asynchronous means for transferring bubbles in and out of said loops for improved performance.
2. Prior Art
Bubble memories on which conditions exist for establishing single wall domains on a suitable magnetic material such as an epitaxial magnetic garnet film on a nonmagnetic substrate are well known. Magnetically soft overlay material in the form of propagate elements are typically arranged in a series of identical storage loops forming a memory organization in which bubbles propagate from one propagate element to another around these loops by the action of an in-plane rotating magnetic field. In this arrangement transfer gates forming part of a write-in means and a read-out means transfer bubbles to and from these loops. Typically, on command, the bubbles will be transferred in parallel into the storage loops from an input track where they are then serially detected as they are propagated through a sensor which detects the presence or absence of a bubble and generates a signal as a binary "1" or a binary "0" data bit.
Although the bubble memory systems employing the storage loops of the type described have numerous economic and operational advantages, there are major shortcomings in the systems. Since a block of data bits in the form of domains are transferred serially to a position alongside the storage loops to be transferred in parallel into the loops at the appropriate time, a block of data bits must wait until all of the prior data bits in the input line are transferred into the loops. Similarly, data bits transferred out at the appropriate time in parallel from the storage loops must wait until all the prior block of data bits has been transferred serially to the sensor. While it is possible to read data from a bubble device during a write operation exact synchronization of the input/output tracks and the storage loops must take place. Also, in systems that do not employ something like swap gates, it is not possible to clear a position in the storage loops for the entry of data if the output track contains data bits.
All of this, of course, increases the steady state random access time for the bubble memory.
Accordingly, it is an object of this invention to improve the steady state random access time of a bubble memory.